Stirlingengineforum.com

VincentG wrote: ↑Tue Feb 21, 2023 4:10 pm

Tom Booth wrote: ↑Sun Feb 13, 2022 2:46 pm The point is, the heat source for the engine is heated plates or vanes that are encapsulated in a very close tolerance heated enclosure with slots the vanes or plates fit into.
A cam controls when the vanes or hot metal plates will drop or slide out or down, out of their slots in the heating unit, into the air filled space, quickly and effectively heating ALL the air at once.

This is exactly what I have thought in the past. It should be the BEST theoretical way to go about it...only problem is I cant think of a way to make this design easy to duplicate and reliably leak free. I do however think I came up with a suitable alternative solution. I will update my post with what I come up with.

Thanks for reminding me about that post/idea, I had forgotten about that, and welcome to the forum, Also looking forward to seeing the progress on your engine.

I've been thinking about the stationary LTD regenerator I just put together and tested.

One problem or issue I have with it is its exposure to the outside ambient air. Why I have the engine surrounded by an insulating blanket
Potential heat loss, and I don't want to have to keep the engine wrapped in a blanket.

So I may combine the idea of a stationary regenerators with the old regenerative displacer with holes cut in the displacer:
But instead of trying to stuff the holes with regenerator material, stationary columns could go inside the holes like so many smoke stacks and the displacer could rise up and down around them driving the air up and down through the stacks without having to lift the heavy regenerator material while also avoiding having the regenerator directly exposed to the outer wall of the engine.

The main problem with this arrangement would be the close tolerances needed and possible binding due to misalignment.

Maybe rather than a styrofoam type floppy displacer something like a rigid plastic or acrylic would have less tendency to bind.

I'm still not entirely convinced though, that a regenerator, in general, serves much purpose other than trapping heat and potentially reducing power, though experimentally, the regenerator does seem to improve performance, at least sometimes.

It may just be that heat is being underutilized. Better than a regenerator might be simply a larger bore piston for more power output to utilize more heat.

It is my thought that the regenerator is simply a bandaid for inadequate heat transfer at the hot and cold ends. Maybe I am dense but I never quite understood the logic that "heat is being wasted on the gas" without a regenerator, as is so often stated in videos that describe the stirling cycle.

Having recently discovered the 25kw Ltd Stirling generator from coolenergy, I am in awe at the potential of these machines.

VincentG wrote: ↑Wed Feb 22, 2023 5:25 am ...

Having recently discovered the 25kw Ltd Stirling generator from coolenergy, I am in awe at the potential of these machines.

I agree, but am a bit cynical. Yes, these engines have great potential but coolenergy made a long term exclusive deal with the utility "Edisun" so you will likely only see those engines running on waste heat from oil refineries and the like for many years to come.

I would love to be proven wrong, but that has been the pattern. Yes these engines exist, but sadly, not for us little people, if we want one we have to build our own out of scrap metal or something.

Hopefully that will change, but I'm not keeping my fingers crossed.

I/we are certainly no match for the engineering might of a large company but I believe there is a practical way to get there. Unfortunately anything that is truly green and that effectively solves issues is not profitable enough to be adopted for consumerism.

VincentG wrote: ↑Wed Feb 22, 2023 8:42 pm I/we are certainly no match for the engineering might of a large company but I believe there is a practical way to get there. Unfortunately anything that is truly green and that effectively solves issues is not profitable enough to be adopted for consumerism.

Well, personally, I think anyone and everyone would, if nothing else, LOVE to own a fuel agnostic emergency generator. A generator to take on camping trips that can run on sticks and twigs etc.

I would have gladly paid any reasonable asking price for such a generator, any time in the past 15 years since back when I was living off the grid up to today. I don't think I'm alone there.

Not profitable enough?

I think it is just much MUCH more profitable not to market to the general consumer.

Not profitable enough?

I think it is just much MUCH more profitable not to market to the general consumer.

Agreed.

VincentG wrote: ↑Tue Feb 21, 2023 4:10 pm

Tom Booth wrote: ↑Sun Feb 13, 2022 2:46 pm The point is, the heat source for the engine is heated plates or vanes that are encapsulated in a very close tolerance heated enclosure with slots the vanes or plates fit into.
A cam controls when the vanes or hot metal plates will drop or slide out or down, out of their slots in the heating unit, into the air filled space, quickly and effectively heating ALL the air at once.

This is exactly what I have thought in the past. It should be the BEST theoretical way to go about it...only problem is I cant think of a way to make this design easy to duplicate and reliably leak free. I do however think I came up with a suitable alternative solution. I will update my post with what I come up with.

This is a similar concept using fins or rods dipped in hydraulic fluid to make a perfect air tight seal around the fins. Personally though, I don't consider isothermal heat transfer a particularly "ideal" goal to be shooting for

The video is a few years old and I have no idea if this project ever got off the ground.

https://youtu.be/k4F9tzQHELY

Edit: It just hit me. What about ferrofluid magnetic seals?

I sent for a small bottle of ferrofluid I intended on using for some experimenting but still haven't gotten around to it.

We have been gradually renovating our old house we live in, but have yet to insulate the attic, which, being above the bathroom, the ceiling of which is not insulated yet either, the bathroom is often quite cold.

As part of our measures to remedy the situation, we installed sockets in the ceiling for some heat lamps.

Well, the hardware store was out of infrared bulbs. All they had was these things:
I thought that would be great, just heat without the annoying red light.

Well, that didn't work out. These particular ceramic heaters are apparently intended to mimic the warmth of a mother hen brooding chicks. You can't really feel any heat unless within about 3 inches. Our bathroom ceiling is about 8 feet.

So we went to a different hardware store and got some real heat lamps. They even had some nice clear ones that seem to emit regular white light.

Anyway, I was left wondering what to do with the ceramic heaters, and so came up with this idea:

https://youtu.be/JhC5V4NK6Ic

From there, that looked so nice and interesting, now I'm having all kinds of ideas for Stirling engine Home Decor.

I know, having a Stirling engine as a lamp you have to plug in kind of defeats the purpose, but oh well, looks kind of cool anyway.

Thats a cool idea Tom. It would be a neat way to add some character to a room. This was often a point made by those who had an Ericsson hot air engine way back when.

I asked my wife what she thought of the idea of a Stirling engine lamp.

Surprisingly she said she thought that was a great idea.

I said Really?

She's not generally all that enthusiastic about my various Stirling engine projects, but she really seemed to think this was a fantastic idea. Then she said:

It would be great if there was a power failure, for some emergency back up lighting, and maybe to charge a cell phone.

So,... I had to explain that I meant a lamp that you plug in. The Stirling engine would just run on the heat from the light bulb.

She just looked at me like I was stupid. "Well, I guess that would be good too" but obviously disappointed with that response.

So then we had a long conversation about the practicality of a Stirling engine lamp that used some alternative fuel... Alcohol?, Kerosene? Lamp oil? A candle?

Well that would be possible, It might be popular with the local Amish community. They actually do use electric lamps with rechargeable batteries in the base. Then they have to recharge the batteries with a big diesel generator every so often.

Using a candle of kerosene lamp to run a Stirling engine to power an electric light seems a bit silly to me also, but maybe. Could the heat from a candle to run a Stirling engine to run a generator to light some LED's produce more light than the candle itself?

Well, Estelle pointed out that the candle or whatever could be enclosed so it would be safer.

Maybe a Stirling engine table lamp that can operate from the heat from some toe warmers?

https://youtu.be/vWISDtKSAqQ

VincentG wrote: ↑Thu Mar 30, 2023 9:25 am Thats a cool idea Tom. It would be a neat way to add some character to a room. This was often a point made by those who had an Ericsson hot air engine way back when.

Maybe not such a bad idea. I just found this on Etsy:
It's an actual kerosene lamp that uses thermoelectric to light up some additional light bulbs.

But seriously? Eleven THOUSAND dollars?

Tom Booth wrote: ↑Thu Mar 30, 2023 8:34 pm
It's an actual kerosene lamp that uses thermoelectric to light up some additional light bulbs.
But seriously? Eleven THOUSAND dollars?

That is indeed NOT a reasonable price.

There is one thermoelectric-powered camping equipment which somehow has some popularity:
Biolite stove
The cost is 149.95USD.
[Official site] : https://www.bioliteenergy.com/products/campstove-2-plus
It's a compact wood gas stove combined with a thermoelectric plate and battery.
The electricity it generates is quite low(3W), almost a gimmick in my opinion.
But still it survived in the market and has its second generation product developed thanks to the thriving market of outdoor recreation.

It showed a chance for Stirling engines to become a part of consumer products and not confined in the industrial domain.

A Stirling engine can easily outperform thermalelectric plates when it comes to efficiency.
Of course the engine must be compact and light enough.

There are already some similar products available in Japan.
Here's one example:
Rocket stove Stirling power generator by MomoseMD( 百瀬機械設計株式会社 ) [picture]


Here's a YouTube footage video:
https://youtu.be/3h8mTE6VVgQ

It features 100~200W electrical output and a plate for cooking.
The fuel can be bamboo, wood, or other biomass fuels.
It looks quite nice to me.
But it is not compact enough to be a desirable camping equipment.
In off-grid area, this might come in handy, especially in Japan where isolated mountain areas and islands covered a large portion of her territory.
And yet it did not make a significant impact on the global market.
In fact the company was closed down in 2019 by the owner due to his health concern.

If this rocket-stove-based system can be lighter and more compact, it will have potential to become a desirable camping/off-grid equipment.
The need for a electrical motor to generate electricity is in fact not a disadvantage.
A thermoelectric plate can only do one thing: turning temperature difference into electricity or vice versa.
A motor can create actual power, both electrical and kinetic.
Even if you are in the middle of nowhere and your gas lighter run out of gas, you can still light a fire with two electric wires by cranking that motor manually:
https://youtu.be/Oq6zvRJp-fk
Then you can move that fire in the rocket stove, get decent amount of electricity for your phone/lamp and heat to cook your meal.

gitPharm01 wrote: ↑Fri Mar 31, 2023 5:59 pm ...

A Stirling engine can easily outperform thermoelectric plates when it comes to efficiency.
Of course the engine must be compact and light enough.

...
If this rocket-stove-based system can be lighter and more compact, it will have potential to become a desirable camping/off-grid equipment.

That rocket stove engine appears to require a rather bulky cooling system with hoses and radiator.
In my opinion, based on experiments, I think a redesign might very well eliminate that while instead utilizing the "waste heat" going into making hot water instead go towards powering a larger generator.

Time will tell. If I can get busy and actually construct something that is not just a toy.

I find myself wondering what my little LTD might have generated on 100 watts of heat with scarcely any apparent "waste heat" before it melted down.

After seeing the "laminar flow" in a so-called, thermoacoustic engine, I've been thinking along the lines of using the venturi effect to entrain air like a reverse air amplifier.

An air amplifier puts compressed air in through a side port but the venturi effect draws air in from a side port, the entrainment of additional fluid takes place in either case.


https://youtu.be/Wokswr_KHXQ?si=R16x-65VsGvmTh5G

https://youtu.be/HWnS287qlM8?si=4aEsN2gQpjQ7DEst

https://youtu.be/cpmEQctfqcI?si=1P19jfbx6n2eDshS

Of course, I first learned about the venturi effect in High School in small engine repair class, since this is how most lawnmower carburators work to draw gas from the gas tank into the air intake stream.

The dilemma however is, if you create an air amplification effect in the power cylinder by entraining extra air during the power stroke, this extra air really has nowhere to go, so there probably needs to be an exhaust port in the power cylinder near BDC, like a Manson engine.

Don't know that this would actually work, but it doesn't amount to much more than drilling a few holes. Maybe three or four for entrainment at the nozzle and a few more holes at the end of the power cylinder.

Probably some check valves at the air inlet ports to prevent air being pushed back out through the venturi ports during the compression stroke.